Wastewater from tapioca processing factory containing high COD (11,077-19,083 mg/l), SS (4,180-7,600 mg/l) and low pH (4.33-5.60) still causes heavy pollution to receiving water in South Vietnam. Closing the water circuit in the tapioca industries represents a very attractive option for eliminating pollution problems and the reuse of treated wastewater and solid wastes. The investigated and presently occasionally already implemented system consists of primary sedimentation tank, anaerobic treatment using UASB-reactors, aeration tanks using attached growth reactor and oxidation ponds system. Under laboratory conditions, organic loading rates applied in UASB-reactors are up to 40,35 kg COD/m3.d with treatment efficiency of 90-95%, reducing the COD concentration from up to 13,449 mg/l to 624-780 mg/l. The final effluent COD (sol.) after treatment in the pond system operated at hydraulic retention time of 12-20 days is lower than 10 mg/l. This effluent is suited very well either for use in agriculture or in the factory.

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